Re: sata promise and software raid5...

[evan-lkml]

You need to test all the disks running at once, this should give a much
clearer picture of how the system will perform with a raid volume.  a
simple test is like so:

-> hdparm -t /dev/sda2 & hdparm -t /dev/sdc2 & hdparm -t /dev/sdc2 &
hdparm -t /dev/sdd2

This will get them all going at once, but may jumble the output a bit.

Evan


On Wed, May 26, 2004 at 03:46:57AM +0400, Andrey Nekrasov wrote:
> Hello,
> 
> controller - Promise SATA 150 TX4, linux 2.6.7-rc1-bk1, HDD Maxtor
> 250Gb (x4)
> 
> Why so slowly reads (and writes) with software raid5?
> 
> gnome:~ # hdparm -t /dev/sda2
> 
> /dev/sda2:
>  Timing buffered disk reads:  148 MB in  3.01 seconds =  49.16 MB/sec
> gnome:~ # hdparm -t /dev/sdb2
> 
> /dev/sdb2:
>  Timing buffered disk reads:  148 MB in  3.02 seconds =  49.01 MB/sec
> gnome:~ # hdparm -t /dev/sdc2
> 
> /dev/sdc2:
>  Timing buffered disk reads:  148 MB in  3.03 seconds =  48.90 MB/sec
> gnome:~ # hdparm -t /dev/sdd2
> 
> /dev/sdd2:
>  Timing buffered disk reads:  144 MB in  3.00 seconds =  47.96 MB/sec
> gnome:~ #
> gnome:~ #
> gnome:~ # hdparm -t /dev/md0
> 
> /dev/md0:
>  Timing buffered disk reads:   64 MB in  3.12 seconds =  20.52 MB/sec
> gnome:~ #
> 
> 
> gnome:~ # cat /etc/raidtab
> raiddev /dev/md0
>         raid-level              5
>         nr-raid-disks           4
>         nr-spare-disks          0
>         persistent-superblock   1
>         parity-algorithm        left-symmetric
>         chunk-size              1024
> 
>         device                  /dev/sda2
>         raid-disk               0
> 
>         device                  /dev/sdb2
>         raid-disk               1
> 
>         device                  /dev/sdc2
>         raid-disk               2
> 
>         device                  /dev/sdd2
>         raid-disk               3
> 
>         
> bye
> --
> 
> 
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